I have a dataset with one dependent variable and several independent categorical variables.

I want to explore the amount of variability each of the independent variables explain in the dependent variable.

This can be done by entering all the variables in a one-way ANOVA and calculating the proportions of explained variability of each factor (SSeffect / SStotal).

However, I am also interested in partitioning the proportion of explained variability of a specific independent variable between the different levels of that variable to see if some levels of a factor have more effect on the dependent variable than others.